Project 4 is set on an offshore oil rig in the Pacific Ocean, somewhere between Australia and the Philippines. Now defunct and abandoned by corporations many years prior, the rig has been repopulated and transformed into a hub for travelling traders, scavengers and fishermen in the area.

The decommissioning of other oil rigs around the Pacific, as well as the sealing of their oil wells, has given rise to a network of artificial reefs developing on their underwater supports over time, supporting the growth of aquatic populations and fishing hotspots. As a result, the oil rig, nicknamed the "ShigRig" by locals, serves as a popular stop for fishermen to unload and trade their goods, while scavengers who collect resources from sunken cities and crashed cargo ships sell their wares in the rig's varied shops.

On the main deck of the oil rig is a marketplace populated by small stalls offering a variety of goods, while shops entrenched into repurposed interior regions line the inner decks of the platform. Below the platform lies a floating market dotted with the fishing and trading boats of merchants and nomads; some regulars, who consider the platform their central hub, and others who pass through the area during long voyages at sea.